Rectifying column



W.LACHMA NN RECTIFYING COLUMN Filed Jan. 5. 1921 Sept. 30 1924.

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Application filed Jaimary 3, 1921. Serial fin. 434,835.

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To all whom it may concern Be it hown that l, WALTER LAOHMANN, acitizen of the German Republic, residing at l Wormserstrasse, Dresden, Saxony, Grermanyfhave invented certain new and useful lmprovementsin ltectifying Columns, of which the following is a specification,-

and for which he has'filed an application for patent in Germany under date of February 15,1917. I

Liquid oxygen, 80% .to 90% pure, for blasting purpbses in mines has hitherto been produced by causing .a'rectitying column to" operate in such a manner-that the separated product obtained at the bottom. oi thecolumn is lliquid oxygen of the desired purity. 4

The present invention relates to a rectitying column which is adapted to produce from a mixture oi nitrogen and oxygen not only a liquid out the above-mentioned. kind which is rich in oxygen, but also oxygen ct.

a quality worth compressing, so that in industr al establishments one and the same fractional distillation plant may be used for.

obtaining blasting air and at the same time oxygen of a high degree of purity for autogeneous welding and cutting. For the sake of brevity it will be assugned hereinafter that the mixture of nitrogen and oxygen dealt with is air. instead or the reciti-c lying column operating to produce pure gaseous oxygen it may be caused to also produce'oiq gen in a liquid form.

since the percentage or oxygen in the;

liquid trickling dhwn the column increases during its passage from the topto the bot-' tom, the said result may be brought about \by extracting liquid from the column at the particular part midway between the and bottom where the composition of the quid renders. it suitable for use as blasting air,

while pure oxygen is extracted at the -bot-" tom. of the column. Gentrary to expectation this extraction of liquid from the mid dlepartof the column does not cause any dificulties in operating with'the column.

A constructional form of a column in accordance with the invention is shown in VB1'-:

tical section in the drawing. lin reality the;

hollow spaces in the column are furnished with ertoratedplates or [glass beads and the lihe, or with any other suitable rectitying arrangement which is omitted in the drawing in order to render the illustration clearer and simpler. In general the'opera tion'of the .column is similar to thatdescribed in the patents of Hazard and Flamand British Patent No. 26,720 of 1908, Fig. 5, and French PatentNo. 394c,881, Fig. 5) whose process is very similar to the known process of Claude. In the former, two processes are combined, viz, 1, the process of heating with the air of the atmosphere, which is limited to 'the bottom end of the column, or distributed over any desired part of its height, and 2', the preparatory separation of the air, viz, in the part a while the final products'are obtained in the part b of the column. Hence the separation of the constituents of the air commences in the chamber a: a-nd'finishes in the chamber b. in the-chamber 0a a fraction 3 containing 30 to per cento'i' oxygen is produced and liquefied and then conducted into the actual rectifying column b at its middle portion. lln addition to this a fraction 5 composed of pure nitrogen is forced irfa liquid form up to the top end of the column b so as to enable pure nitrogen to be obtained. Besides, the chamber 6 is provided at its lower end with two outlets c and d for. gaseous oxygen 6 and liquid oxygen 7 respectively, and at its upperend it has an outlet 6, iornitrogen 8. The separating columns is also provided at its lower end with. an'outlet f forthe liquidv 9 that is identical with the product 8 obtained by the preparatory separating or condensing process. 2 is liquid nitrogen produced by coolin and thus condensing the nitrogen of the ottom chamber a, and t is also liquid nitrogen.

An important feature of the present invention consists in the chamber I) being provided with a compartment 9 from which actual rectifying column.

-of a considerable .size. Considerable quantities of blasting air'can then be taken out whenever such air is requi or when the said compartment is full and is to be I emptied. But blasting air may also be Z for blasting air 11, Thecistern is may be open at the top or, as shown in the drawing,

' closed and equipped with an upper air discharge valve m which may also serve as a' pressure balancing valve, so that the valve '11 could be dispensed with.

After its discharge and expansion the percentage of oxygen in the blasting air 11 may be lncreased by mixing it with liquid I oxygen taken from the tap (2. But above all the said percentage may be reduced by mixing the blasting air with the liquid product 9 obtained in the preliminary vseparation process To enable thevoxygen or preliminary liquid product to be-tapped off as required for making the said mixtures, the evaporator of the chamber 6 and the lower end of the preliminary separation chamber a, are equipped with the aforementioned taps d and 7 respectively. But

taps of small cross section such as those which have been used occasionally merely for drawing off samples would not do for this purpose. I q a A means for quickly and easily increasing the percentage of oxygen contained in the blasting air before-it is tapped ofi from the compartment 9" is the followingz' The discentage 0 .charge of oxygen (6 or 7) that is ready for use,'is reduce to such an extent that' most of the oxygen 'in the column streams up- Wards, and 1n so doing thoroughly heats the compartment g and its contents, thus causing nitrogen to evaporate and the peroxygen contained in the liquid to be increased as desired: The heating of p the compartment 9 may-be carried out in the .following ways By blowingthe' vapors through the chamber 9 they are brought into direct contact with the liquid contents of the said chamber. Heat will then be given ofi in the desired manner and a perfect fractional evaporation will take place. Tothis end the upwardly extending pipes n provided inthe compartconducted through the lower chamber of thement 9 are equipped with tubular hoods 0 closed at the top. and having their bottom ends low enough to dip under the lowest level to which the liquid sinks. In order to enable a certain quantity of liquid to be column also, a pipe p is provided which leads from this chamber and issues in'chamber .9 just above its bottom; pipe 37 is equipped with. a cock g by which the amount of liquid that passes into the lower chamber can be regulated. This amount will remain almost constant regardless of the level of the liquid, because as the latter rises the counter-pressure in the lower chamber will increase in the same proportion.

The pipes n that are coveredwith hoods may also serve to constantly conduct a sufiicient quantity of vapors from the chamber situated beneath the com artment 9 into the chamber above it. This, owever, would involve the slight disadvantage, that the vapors would have to overcome a counter-pressure that corresponds to the level of the liquid in g, and that varies in accordance with this level. the liquid amounting to-30 cms. for instance this counter-pressure would be approximately 1/30 of an atmosphere. This slight drawback may be eliminated by using the said pipes at only for heating in the de scribed manner whenever this should prove necessary and by making provision for the passage of vapor, which is required for the rectification process, by equipping the column with a permanently fitted pipe (or pipes) 1- t'hat is open at both ends and either forms a side passage as indicated, or extends in a straight line from the chamber beneath 9 through the whole compartment '5; parallel to the longitudinal axis of 'the column. Means, such as a valve or a throttling member 8 must be rovided for closing this pipe r so as to em. le the At a level of' Pa n to be put into operation when require i It might be supposed that a method of reducing thepercentage of oxygen contained in the liquid 10 of the/collecting compartment 9 would be to increase the discharge of the product 6 or 7 (oxygen) obtained beneath the compartment. ut generally speakin this would be a great mistake, because. y this increased discharge thelower oxygen 6 (or -7) would become so mob in nitrogen as to be useless. Thus the only proper way to obtain a liquid comparat vel poor in oxygen is that already descrlbe viz, to mix the blasting air 11 with the liquid product 9 obtained by the prelimlnary process of separation.

The above description does not apply only to blasting air but also to liquid air IlCh 1n,

oxygen, as that employed in coal mines in case of fire-damp explosions and for breathing"purposes on-air-ships and aeroplanes at great altitudes, and to liquefied gas containing a :high precentage of oxygen, but

whose oxygen component is to be increased through long storage and the inevitable evaporation resulting therefrom to such an extent as to render it serviceable for technical purposes, as for the autogenous welding and cutting of metals for which oxygen may be used which v or conducting it under a low pressure to the point of consumption, a rectifying columnproduces at its bottom chambers a liquid rich in oxygen but still containing 5 to 15% of nitrogen, and this liquid may be kept and dispatched in the known vessels for storing liquid air, in which the oxygen component of the liquid increases automatically through the inevitable evaporation that takes place. Through the nitrogen component of the liquid being. large when the liquid'is first filled into the carrying vessels the vapors rising therefrom will also be rich in nitrogen and hereby the losses of oxygen, which in this case is the more valuable product of separation, are considerably diminished. If desired, the evaporation alluded 'to can be accelerated, as by inserting metal rods into the liquid, which will then. conduct an increased amount of warmth into it from the atmosphere.

It will be obvious that my invention is not only applicable for the production of blasting air and the like from mixtures of nitrogen and oxygen, but that it may also be used without change for separating the components of other gas mixtures which arehard to liquefy.

I claim:

1. A rectifying column for separating the components of gas mixtures, comprising a vessel divided into a rectifying chamber and a preparatory separating chamber disposed below said rectifying chamber, said separating chamber having near its upper end a centrally perforated partition forming a liquid compartment and said rectifying chamber being subdivided into an upper compartment and a lower compartment,

said upper compartment being adapted to contain a liquid, a pipe communicating with the separating chamber adjacent to the bottom thereof and with the upper compart: ment of the rectifying chamber at approximately the center of its height, a pipe communicating with the liquid compartment at the upper end of the separating chamber and with the upper endof said upper com partment, a condenser-vaporizer communicating wlth the separating chamber above its upper liquid compartment and extending into the lower compartment of the rectifying chamber, warmmg means extending into the upper compartment from the bottom thereof, said warming means being adapted to conduct vapors from the lower compartment into the upper compartment through a liquid contained in said upper compartment, a by-pass communicating with the uppercompartment near its bottom and with the lower compartment near the top thereof, a. by-pass communicatin with the lower compartment near the top thereof and with the upper compartment at a point remote from its bottom. valve-controlled outlets for drawing 0d the liquid from the lower end of the separating chamber and the lower compartment of the rectifying chamber, a valve-controlled outlet for drawing of the gas from said lower compartment, and an inlet for supplying the gas mixture to the separating chamber. w

2. A rectifying column for separating the components of gas mixtures, comprising a vessel divided into a rectifying chamber and a preparatory separating chamber disposed below said rectifying chamber, said separating chamber having near its upper end a centrally perforated partition forming a liquid compartment and said rectifying chamber being subdivided into an upper compartment and a lower compartment, said upper compartment being adapted to contain aliquid', a pipe communicating with the separating chamber adjacent to the bottom thereof and with the upper compartment of the rectifying chamber at approximately the center of its height, a pipe communicating with the liquid compartment at the upper. end of the separating chamber and with the upper end of said upper compartment, a condenser-vaporizer communicating with the separating chamber above its upper liquid compartment and extending into the lower. compartment of the rectifying chamber, warming means extending into the upper compartment from the bottom thereof, said warming means being adapted to conduct vapors from the lower compart ment into the upper compartment through the liquid contained in said upper compartment, a by-pass communicating with the partment near its bottom and with said storage receptacle,

In, testimony whereof I have signed thls specification .in the presence of two witnesses.

, WALTER LACHMANN. Witnesses:

Dr. HERMANN HAHLE, D. VOLKMAR Kmrrnn. 

